This invention relates to visual display panels for use in television receivers, monitors, computer readouts, and other video systems; or more specifically this invention is designed to replace the conventional cathode ray picture tube.
The efforts so far expanded to replace the cathode ray tube with a less complex and cumbersome panel are legion. In particular, a multitude of innovative displays have recently been disclosed based on light emitting diode, electroluminescent, laser, and gas discharge light emitting mechanisms.
The more prevalent cathodoluminescent light emitting mechanism, however, is often specified for display panels, as this continues to be a proven technique for video displays. In addition, the common "postdeflection acceleration" technique permits low voltage addressing of a cathode ray display, with brightness provided by a subsequent acceleration section, as contrasted with the typical gas discharge or electroluminescent display, for example, wherein the full picture element power must be controlled by the address circuitry.
This reasoning has led to many attempts at flat cathode ray panels, so far with less than ideal results. Two repeated failings of current proposals are burdensome addressing schemes, and manufacturing difficulties resulting from the complexity of these designs. The need to provide a simple addressing process and a low cost structure are fundamental to the achievement of a practical device for use by the general public.
As the most direct mode of addressing is by the well known "x-y matrix" a third problem that arises is the need to provide a large area electron source for the panel. Several sources have been proposed to meet this need, such as nets of thermionic emitters or various cold cathode devices; most of these add hinderances of cost or short useful lifetimes.
In recognition of these problems, a display panel is proposed based on the phenomenon of optical feedback as an electron source. Recent developments in photocathode and phosphor research have advanced this well known mechanism as a prime source of electrons for flat display devices, although current display proposals based on this effect have so far fallen far short of a practical device.
In the matter of addressing, the "self-shifting" or bussed cathode is without doubt the preeminent technique, offering greatly simplified panel construction, and vastly reduced external circuitry requirements. This process has, of late, been applied in several forms, such as attempts to produce shift registers using a photoconductive-electroluminescent active element (the name "lumistor" was suggested for this device), or more commonly in the so-called "self-scan" gas discharge display, and its many sub-variants. Because of switching speed problems and other limitations, however, this process has so far failed to achieve practical results in large display devices.